In a typical motor vehicle suspension, a damper is provided that exerts a damping force on relative movement between sprung and unsprung masses of the vehicle. The damping force provided by the damper is related to the relative speed between the sprung and unsprung masses according to a characteristic force-velocity profile. Currently, motor vehicles are available with variable damping systems that allow real-time control of the damper force-velocity profile, allowing switching between two or more profiles. Descriptions of example systems are found in U.S. Pat. Nos. 5,071,157, 5,062,658 and 5,062,657, assigned to the assignee of this invention.
It is known to provide vehicles with variable force dampers controllable between three force curves in an adaptive manner. It is also known to provide a vehicle suspension system with a variable force damper controllable between force curves in an almost continuous manner, in non-real-time.
U.S. Pat. No. 5,282,645, assigned to General Motors Corporation, describes a valve for use with a suspension system having a controllable damper that is capable of providing continuously variable damping control with a fast, real-time, response.